The present invention relates generally to sealed bags and more specifically to a sleeveless valve bag or partially closed open mouthed bag.
Currently, there are two basic types of bags being used in the industrial packaging field; namely, the valve bag and the open-mouth bag. A serious limitation of the valve bag is the inability to achieve a positive closure to prevent leakage and sifting of the product from the bag, to prevent insect infestation and to obtain a hermetical seal. To improve the closure of the seal, the valve opening may be made smaller, but this reduces the filling speed. Thus the designer of valve bags must weigh the positive closure of the valve against the filling speed. A typical valve bag 15 of prior art is illustrated in FIG. 1 having a valve sleeve 16 extending between the interior of the bag and the exterior. The axis of the valve sleeve 16 is on the side of the bag or along the lateral axis. The lateral valve bags may be filled horizontally as is the case in the United States, or vertically as is the case of some foreign countries. Either method of filling a lateral valve bag does not make effective use of the volume of the bag because of the angular repose of the product filling the bag.
Thus there is existing need for a valve bag with an opening large enough to insure maximum filling speed, located to make effective use of the filling rate and bag volume and capable of easily and conveniently being hermetically sealed.
The open mouth bags are either tube style or pinch style wherein the latter provides a better seal. The pinch style, open mouth bag is a gussetted open mouth bag that has a specific type of closure. This closure can, when properly made, provide a hermetical seal. A serious limitation of this specific open mouth bag is that the entire top of the bag is open and after the filling operation is completed, the bag top must be reformed and flattened for entry into a closing and sealing machine. A typical example of prior art open mouth bags in the open and sealed condition are illustrated in FIGS. 2 and 3 respectively.
Due to the nature of the bag construction, the bag top must be level when entered into the closing machine, within a narrow angular tolerence, to insure that the closing operation along the complete bag top width is accomplished properly and the hermetical seal actually obtained. In addition to the level requirement, there must be a wrinkle and warp free bag top surface in the closure to assure a heremetical seal. Since the complete bag top must be reformed and flattened and since the bag tends to be rounded from the material contained, warpage and wrinkles can easily be generated during the reforming operation. To minimize this condition, the level of material, in relation to the bag top edge (known as freeboard), must be low (approximately 9 inches from the top of the bag) to insure a quick, easy and reliable closure and seal. This relationship between the fill line and fold line is illustrated in FIG. 4. Clamps are also schematically shown which hold the gussets formed at the top edge and maintains the top edge horizontally to assure a completely sealed closure. As can be seen, the devices of the prior art in order to assure a perfect seal, drastically reduce the fill opening.
Thus there exists a need for a tube or pinch style, open mouth bag having a large fill opening for a given linear length of top edge, a wide tolerance for bag top level condition for closing and sealing, and reducing the amount of freeboard and consequently paper needed to effect a sealed closure for a given volume of product.